CN108476546B

CN108476546B - Method and apparatus for establishing bearer for transmission of user data

Info

Publication number: CN108476546B
Application number: CN201680077128.5A
Authority: CN
Inventors: 边大旭; 柳珍淑; 金兑勋; 徐健; 金鉐中
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2015-12-29
Filing date: 2016-12-27
Publication date: 2021-11-09
Anticipated expiration: 2036-12-27
Also published as: KR102051552B1; US20190021023A1; US10616789B2; KR20180071365A; CN108476546A; EP3399831B1; EP3399831A4; EP3399831A1; WO2017116115A1

Abstract

A method of establishing a bearer for user data transmission in a user plane-based cellular Internet of things (CIoT) in a wireless communication system and an apparatus supporting the same are provided. The base station receives a Tracking Area Update (TAU) request message from the terminal, sends an initial UE message including the TAU request message to a Mobility Management Entity (MME), receives a downlink NAS transport message from the MME, the downlink NAS transport message including a recovery indication, and can send the UE context recovery request message to the MME based on the recovery indication.

Description

Method and apparatus for establishing bearer for transmission of user data

Technical Field

The present invention relates to a wireless communication system, and more particularly, to a method of a base station configuring a bearer for transmission of user data in a user plane-based cellular internet of things (CIoT) in a wireless communication system and an apparatus supporting the same.

Background

In recent years, a machine-to-machine/internet of things (M2M/IoT), which connects all the respective objects through a network to help acquire and transmit necessary information anytime and anywhere, thereby enabling it to provide and use various services, has become a major issue in the next-generation communication market.

Although the early M2M started primarily from sensors and RFID networks in local areas, various wired/wireless networks could be used with the growing diversity of purposes and application features. Recently, M2M based on a mobile communication network receives increasing attention in terms of mobility of objects, a wide service area including not only islands and mountains but also oceans, simplicity of network management and maintenance, security for reliable data transmission, and assurance of service quality. Therefore, since the feasibility of M2M was studied from 2005, the 3GPP has been going on a comprehensive standardization project named "Machine Type Communication (MTC)" since 2008.

The 3GPP views machines as entities that do not require direct human manipulation or intervention, and defines MTC as a form of data communication involving one or more machines. Typical examples of such machines include smart meters and vending machines equipped with mobile communication modules. Recently, with the introduction of a smart phone that performs communication by automatically connecting to a network, a mobile terminal having an MTC function is considered to be in the form of a machine according to a location or condition of a user without any user operation or intervention. In addition, a gateway type MTC device connected to an IEEE 802.15 WPAN-based subminiature sensor or RFID is also considered.

The internet of things (IoT) is a future infrastructure and service for future information communication, where all objects are connected to the internet to communicate directly with each other. Although IoT is necessary to improve quality of life and productivity based on super-interconnected society, IoT is ultimately important as it forms the infrastructure of the country and further forms the central nervous system of humans and the earth. The IoT is in an initial stage that has not yet had an important profitability pattern. However, the market size of IoT, a new paradigm in the 21 st century, is more than 10 times that of the existing cellular communication market, and is expected to grow rapidly. The IoT is roughly divided into IoT (ciot) -based cellular mobile communication and IoT-based non-cellular mobile communication.

Disclosure of Invention

In user plane based CIoT, when a UE in ECM _ IDLE state triggers a TAU procedure, the UE may transmit an RRC connection resume request message including a TAU request and an active flag if UL data exists. In this case, since the RRC connection resume request message does not include "bearer ind. Therefore, in order for the UE to transmit UL data, unnecessary procedures may need to be performed. Further, since the bearer context is not activated, although the MME recognizes that downlink data to be transmitted to the UE exists, the downlink data cannot be transmitted to the UE. Therefore, there is a need to propose improved S1 signaling for the transmission of user data in a user plane based CIoT.

In one embodiment, a method of a base station configuring a bearer for user data transmission in a user plane based cellular internet of things (CIoT) in a wireless communication system is provided. The base station may include receiving a Tracking Area Update (TAU) request message from a User Equipment (UE), sending an initial UE message including the TAU request message to a Mobility Management Entity (MME), receiving a downlink NAS transport message including a recovery indication from the MME, and sending a UE context recovery request message to the MME based on the recovery indication.

The TAU request message received from the UE may be included in the RRC connection resume request message. The RRC connection resumption request message may not include a bearer indication. Suspension of the RRC connection may be prohibited and transmission of the UE context resume request message may be triggered by the resume indication. A recovery indication may be received from the MME if the TAU request message includes an active flag. Recovery indication may be received from the MME if the presence of downlink data to be sent to the UE is identified by the MME

The base station may further include receiving a resume request indication from the UE to request resumption of the UE, and determining whether it is possible to resume the previously suspended RRC connection based on the resume request indication. The recovery request indication may be included in the RRC connection request message. The TAU request message received from the UE may be included in an RRC connection setup complete message. The initial UE message may include a recoverable indication indicating whether the base station is capable of recovering a previously suspended RRC connection. The transmission of the UE context restore request message may be triggered by a restore indication. A recovery indication may be received from the MME if the TAU request message includes an active flag. A recovery indication may be received from the MME if the MME identifies the presence of downlink data to be sent to the UE

The UE may be in an RRC IDLE state.

In another embodiment, a base station for configuring a bearer for transmission of user data in a user plane based cellular internet of things (CIoT) in a wireless communication system is provided. The base station includes: a memory; a transceiver; and a processor connected to the memory and the transceiver. The processor may be configured to control the transceiver to receive a Tracking Area Update (TAU) request message from a User Equipment (UE), to send an initial UE message including the TAU request message to a Mobility Management Entity (MME), to receive a downlink NAS transfer message including a recovery indication from the MME, and to send a UE context recovery request message to the MME based on the recovery indication.

The bearer may be configured.

Drawings

Fig. 1 shows an LTE system architecture.

Fig. 2 shows a control plane of a radio interface protocol of the LTE system.

Fig. 3 shows a user plane of a radio interface protocol of the LTE system.

Fig. 4 illustrates an example of MTC.

Fig. 5 shows a suspension procedure of RRC connection in user plane based CIoT.

Fig. 6 illustrates a recovery procedure of RRC connection in user plane based CIoT.

Fig. 7 shows the MM procedure for TAU in user plane based CIoT.

Fig. 8 illustrates an RRC recovery procedure when a TAU request is triggered according to an embodiment of the present invention.

Fig. 9 illustrates an RRC recovery procedure when a TAU request is triggered according to an embodiment of the present invention.

Fig. 10 illustrates an RRC recovery procedure when a TAU request is triggered according to an embodiment of the present invention.

Fig. 11 illustrates an RRC recovery procedure when a TAU request is triggered according to an embodiment of the present invention.

Fig. 12 is a block diagram illustrating a method of an eNB configuring a bearer for transmission of user data in a user plane-based CIoT according to an embodiment of the present invention.

Fig. 13 is a block diagram illustrating a wireless communication system according to an embodiment of the present invention.

Detailed Description

The techniques described below can be used in various wireless communication systems such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and so on. CDMA can be implemented in a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA-2000. TDMA can be implemented in a radio technology such as global system for mobile communications (GSM)/General Packet Radio Service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA can be implemented in radio technologies such as Institute of Electrical and Electronics Engineers (IEEE)802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like. IEEE 802.16m evolved from IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16. UTRA is part of the Universal Mobile Telecommunications System (UMTS). Third generation partnership project (3GPP) Long Term Evolution (LTE) is part of evolved UMTS (E-UMTS) using E-UTRA. The 3GPP LTE uses OFDMA in downlink and SC-FDMA in uplink. LTE-advanced (LTE-a) is an evolution of 3GPP LTE.

For clarity, the following description will focus on LTE-a. However, the technical features of the present invention are not limited thereto.

Fig. 1 shows an LTE system architecture. Communication networks are widely deployed to provide various communication services such as voice over internet protocol (VoIP) through IMS and packet data.

Referring to FIG. 1, an LTE system architecture includes one or more user equipments (UEs; 10), an evolved UMTS terrestrial radio access network (E-UTRA), and an Evolved Packet Core (EPC). The UE 10 refers to a communication device carried by a user. The UE 10 may be fixed or mobile and may be referred to by other terms such as Mobile Station (MS), User Terminal (UT), Subscriber Station (SS), wireless device, etc.

The E-UTRAN includes one or more evolved node bs (enbs) 20, and a plurality of UEs may be located in one cell. The eNB 20 provides the UE 10 with endpoints of the control plane and the user plane. The eNB 20 is generally a fixed station that communicates with the UE 10 and may be referred to as another term, such as a Base Station (BS), a Base Transceiver System (BTS), an access point, etc. One eNB 20 may be deployed per cell. One or more cells exist within the coverage of the eNB 20. A single cell is configured to have one of bandwidths selected from 1.25, 2.5, 5, 10, and 20MHz, etc., and provides a downlink or uplink transmission service to several UEs. In such a case, different cells can be configured to provide different bandwidths.

Hereinafter, Downlink (DL) denotes communication from the eNB 20 to the UE 10, and Uplink (UL) denotes communication from the UE 10 to the eNB 20. In the DL, the transmitter may be part of the eNB 20 and the receiver may be part of the UE 10. In the UL, the transmitter may be part of the UE 10 and the receiver may be part of the eNB 20.

The EPC includes a Mobility Management Entity (MME) responsible for control plane functions and a System Architecture Evolution (SAE) gateway (S-GW) responsible for user plane functions. The MME/S-GW 30 may be located at the end of the network and connected to an external network. The MME has UE access information or UE capability information, and such information may be used primarily in UE mobility management. The S-GW is a gateway whose end point is the E-UTRAN. The MME/S-GW 30 provides endpoints for session and mobility management functions of the UE 10. The EPC may further include a Packet Data Network (PDN) gateway (PDN-GW). The PDN-GW is a gateway whose end point is a PDN.

The MME provides various functions to the eNB 20 including non-access stratum (NAS) signaling, NAS signaling security, Access Stratum (AS) security control, inter-Core Network (CN) node signaling for mobility between 3GPP access networks, idle mode UE reachability (including control and execution of paging retransmissions), tracking area list management (for UEs in idle and active modes), P-GW and S-GW selection, MME selection for handover with MME change, Serving GPRS Support Node (SGSN) selection for handover to 2G or 3G 3GPP access networks, roaming, authentication, bearer management functions including dedicated bearer establishment, support for common warning system (PWS) including Earthquake and Tsunami Warning System (ETWS) and Commercial Mobile Alarm System (CMAS) message transport. The S-GW host provides various types of functions including per-user based packet filtering (e.g., deep packet probing), lawful interception, UE Internet Protocol (IP) address assignment, transport level packet tagging in DL, UL and DL service level charging, gating and rate enhancement, APN-AMBR based DL rate enhancement. For clarity, the MME/S-GW 30 will be referred to herein simply as a "gateway," but it should be understood that this entity includes both an MME and an S-GW.

An interface for transmitting user traffic or control traffic may be used. The UE 10 and the eNB 20 are connected by means of a Uu interface. The enbs 20 are interconnected by means of an X2 interface. The neighboring eNB may have a mesh network structure with an X2 interface. The eNB 20 is connected to the EPC by means of an S1 interface. The eNB 20 is connected to the MME by means of the S1-MME interface and to the S-GW by means of the S1-U interface. The S1 interface supports a many-to-many relationship between the eNB 20 and the MME/S-GW.

The eNB 20 may perform functions for selection of the gateway 30, routing towards the gateway 30 during Radio Resource Control (RRC) activation, scheduling and transmission of paging messages, scheduling and transmission of Broadcast Channel (BCH) information, dynamic allocation of resources to the UEs 10 in both UL and DL, configuration and provisioning of eNB measurements, radio bearer control, Radio Admission Control (RAC), and connection mobility control in LTE _ ACTIVE state. In the EPC, and as noted above, the gateway 30 may perform the functions of paging initiation, LTE _ IDLE state management, ciphering of the user plane, SAE bearer control, and ciphering and integrity protection of NAS signaling.

Fig. 2 shows a control plane of a radio interface protocol of the LTE system. Fig. 3 shows a user plane of a radio interface protocol of the LTE system.

Layers of a radio interface protocol between the UE and the E-UTRAN may be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of an Open System Interconnection (OSI) model, which is well known in the communication system. A radio interface protocol between the UE and the E-UTRAN may be horizontally divided into a physical layer, a data link layer, and a network layer, and may be vertically divided into a control plane (C-plane) as a protocol stack for control signal transmission and a user plane (U-plane) as a protocol stack for data information transmission. At the UE and the E-UTRAN, layers of the radio interface protocol exist in pairs and are responsible for data transmission of the Uu interface.

The Physical (PHY) layer belongs to L1. The PHY layer provides an information transfer service to a higher layer through a physical channel. The PHY layer is connected to a Medium Access Control (MAC) layer, which is a higher layer of the PHY layer, through a transport channel. The physical channels are mapped to transport channels. Data is transferred between the MAC layer and the PHY layer through a transport channel. Between different PHY layers, i.e., a PHY layer of a transmitter and a PHY layer of a receiver, data is transmitted through a physical channel using radio resources. The physical channel is modulated using an Orthogonal Frequency Division Multiplexing (OFDM) scheme and time and frequency are utilized as radio resources.

The PHY layer uses several physical control channels. A Physical Downlink Control Channel (PDCCH) reports resource allocation on a Paging Channel (PCH) and a downlink shared channel (DL-SCH) and hybrid automatic repeat request (HARQ) information related to the DL-SCH to a UE. The PDCCH may carry an UL grant for reporting resource allocation for UL transmission to the UE. A Physical Control Format Indicator Channel (PCFICH) reports the number of OFDM symbols used for PDCCH to the UE and is transmitted in each subframe. A physical hybrid ARQ indicator channel (PHICH) carries HARQ Acknowledgement (ACK)/negative-acknowledgement (NACK) signals in response to UL transmissions. The Physical Uplink Control Channel (PUCCH) carries UL control information such as HARQ ACK/NACK for DL transmission, scheduling request, and CQI. The Physical Uplink Shared Channel (PUSCH) carries the UL-uplink Shared Channel (SCH).

The physical channel is composed of a plurality of subframes in the time domain and a plurality of subcarriers in the frequency domain. One subframe is composed of a plurality of symbols in the time domain. One subframe is composed of a plurality of Resource Blocks (RBs). One RB consists of a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use a specific subcarrier of a specific symbol of the corresponding subframe for the PDCCH. For example, the first symbol of a subframe may be used for PDCCH. The PDCCH carries dynamically allocated resources such as Physical Resource Blocks (PRBs) and Modulation and Coding Schemes (MCSs). A Transmission Time Interval (TTI), which is a unit time for data transmission, may be equal to the length of one subframe. The length of one subframe may be 1 ms.

The transport channels are classified into a common transport channel and a dedicated transport channel according to whether the channels are shared. DL transport channels for transmitting data from the network to the UE include a Broadcast Channel (BCH) for transmitting system information, a Paging Channel (PCH) for transmitting a paging message, a DL-SCH for transmitting user traffic or control signals, and the like. The DL-SCH supports HARQ, dynamic link adaptation by varying both modulation, coding and transmit power, and dynamic and semi-static resource allocation. The DL-SCH may also enable the use of broadcast and beamforming for the entire cell. The system information carries one or more system information blocks. All the system information blocks may be transmitted with the same period. Traffic or control signals for a multimedia broadcast/multicast service (MBMS) may be transmitted through the DL-SCH or a Multicast Channel (MCH).

UL transport channels for transmitting data from the UE to the network include a Random Access Channel (RACH) for transmitting an initial control message, an UL-SCH for transmitting user traffic or control signals, and the like. The UL-SCH supports HARQ and dynamic link adaptation by varying transmit power and possibly modulation and coding. The UL-SCH may also enable the use of beamforming. The RACH is generally used for initial access to a cell.

The MAC layer belongs to L2. The MAC layer provides a service to a Radio Link Control (RLC) layer, which is a higher layer of the MAC layer, via a logical channel. The MAC layer provides a function of mapping a plurality of logical channels to a plurality of transport channels. The MAC layer also provides a function of logical channel multiplexing by mapping a plurality of logical channels to a single transport channel. The MAC sublayer provides data transmission services over logical channels.

The logical channels are classified into a control channel for transmitting control plane information and a traffic channel for transmitting user plane information according to the type of transmitted information. That is, a set of logical channel types is defined for different data transmission services provided through the MAC layer. The logical channel is located above the transport channel and is mapped to the transport channel.

The control channel is used only for transmission of control plane information. Control channels provided through the MAC layer include a Broadcast Control Channel (BCCH), a Paging Control Channel (PCCH), a Common Control Channel (CCCH), a Multicast Control Channel (MCCH), and a Dedicated Control Channel (DCCH). The BCCH is a downlink channel for broadcasting system control information. The PCCH is a downlink channel that transmits paging information and is used when the network does not know the location cell of the UE. UEs that do not have an RRC connection with the network use CCCH. The MCCH is a point-to-multipoint downlink channel used to transmit MBMS control information from a network to a UE. The DCCH is a point-to-point bi-directional channel used by UEs having an RRC connection that transmits dedicated control information between the UE and the network.

The traffic channel is used only for transmission of user plane information. Traffic channels provided by the MAC layer include a Dedicated Traffic Channel (DTCH) and a Multicast Traffic Channel (MTCH). DTCH is a point-to-point channel dedicated to one UE for the transmission of user information and can exist in both the uplink and downlink. The MTCH is a point-to-multipoint downlink channel for transmitting traffic data from the network to the UE.

The uplink connection between the logical channel and the transport channel includes a DCCH that can be mapped to the UL-SCH, a DTCH that can be mapped to the UL-SCH, and a CCCH that can be mapped to the UL-SCH. The downlink connection between the logical channel and the transport channel includes a BCCH that can be mapped to a BCH or DL-SCH, a PCCH that can be mapped to a PCH, a DCCH that can be mapped to a DL-SCH, and a DTCH that can be mapped to a DL-SCH, an MCCH that can be mapped to an MCH, and an MTCH that can be mapped to an MCH.

The RLC layer belongs to L2. The RLC layer provides a function of adjusting the size of data by concatenating and dividing data received from an upper layer in radio segmentation so as to be suitable for a lower layer to transmit the data. In addition, in order to ensure various quality of service (QoS) required by the Radio Bearer (RB), the RLC layer provides three operation modes, i.e., a Transparent Mode (TM), an Unacknowledged Mode (UM), and an Acknowledged Mode (AM). For reliable data transmission, the AM RLC provides a retransmission function through automatic repeat request (ARQ). Meanwhile, the function of the RLC layer can be realized by using a functional block inside the MAC layer. In such a case, the RLC layer may not exist.

The Packet Data Convergence Protocol (PDCP) layer belongs to L2. The PDCP layer provides a function of header compression that reduces unnecessary control information so that data transmitted by employing IP packets such as IPv4 or IPv6 can be efficiently transmitted over a radio interface having a relatively small bandwidth. Header compression increases transmission efficiency in the radio section by transmitting only necessary information in the header of the data. In addition, the PDCP layer provides a function of security. The functions of security include encryption to prevent third party's inspection, and integrity protection to prevent third party's data manipulation.

Radio Resource Control (RRC) belongs to L3. The RLC layer is located at the lowest part of L3 and is defined only in the control plane. The RRC layer plays a role of controlling radio resources between the UE and the network. For this, the UE and the network exchange RRC messages through the RRC layer. The RRC layer controls logical channels, transport channels, and physical channels with respect to configuration, reconfiguration, and release of RBs. The RB is a logical path for data delivery between the UE and the network provided through L1 and L2. That is, the RB means a service provided for L2 for data transmission between the UE and the E-UTRAN. The configuration of the RB implies a procedure for specifying a radio protocol layer and channel characteristics to provide a specific service and for determining respective detailed parameters and operations. The RB is classified into two types, i.e., a signaling RB (srb) and a data RB (drb). SRB is used as a path for sending RRC messages in the control plane. The DRB is used as a path for transmitting user data in the user plane.

A non-access stratum (NAS) placed on the RRC layer performs functions such as session management and mobility management.

Referring to fig. 2, the RLC and MAC layers (terminated in an eNB on the network side) may perform functions such as scheduling, automatic repeat request (ARQ), and hybrid automatic repeat request (HARQ). The RRC layer (terminated in an eNB on the network side) may perform functions such as broadcasting, paging, RRC connection management, RB control, mobility functions, and UE measurement reporting and control. The NAS control protocol (terminated in the MME of the gateway on the network side) may perform functions such as SAE bearer management, authentication, LTE _ IDLE mobility handling, paging initiation in LTE _ IDLE, and security control for signaling between the gateway and the UE.

Referring to fig. 3, the RLC and MAC layers (terminated in the eNB on the network side) may perform the same functions for the control plane. The PDCP layer (terminated in an eNB on the network side) may perform user plane functions such as header compression, integrity protection, and ciphering.

Hereinafter, an RRC state and an RRC connection procedure of the UE are described.

The RRC state indicates whether the RRC layer of the UE is logically connected to the RRC layer of the E-UTRAN. The RRC state may be divided into two different states such as an RRC connected state and an RRC idle state. The UE is in RRC _ CONNECTED when an RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, and is in RRC _ IDLE otherwise. Since the UE in RRC _ CONNECTED has an RRC connection established using the E-UTRAN, the E-UTRAN can recognize the existence of the UE in RRC _ CONNECTED and can effectively control the UE. Meanwhile, the UE in the RRC _ IDLE may not be identified by the E-UTRAN, and the CN manages the UE in units of area TAs larger than the cell. That is, the presence of a UE only in RRC _ IDLE is recognized in units of a large area, and the UE must transition to RRC _ CONNECTED to receive a typical mobile communication service such as voice or data communication.

In the RRC _ IDLE state, the UE may receive broadcast of system information and paging information while the UE specifies Discontinuous Reception (DRX) configured by the NAS, and the UE has been assigned an Identification (ID) that uniquely identifies the UE in the tracking area and may perform Public Land Mobile Network (PLMN) selection and cell reselection. Further, in the RRC _ IDLE state, no RRC context is stored in the eNB.

In the RRC _ CONNECTED state, the UE has an E-UTRAN RRC connection and context in the E-UTRAN, making it possible to transmit and/or receive data to and/or from the eNB. Further, the UE can report channel quality information and feedback information to the eNB. In the RRC _ CONNECTED state, the E-UTRAN knows the cell to which the UE belongs. Thus, the network can send and/or receive data to/from the UE, the network can control the mobility of the UE (handover and inter-Radio Access Technology (RAT) cell change commands to GSM EDGE Radio Access Network (GERAN) with Network Assisted Cell Change (NACC)), and the network can perform cell measurements for neighbor cells.

In the RRC _ IDLE state, the UE specifies a paging DRX cycle. Specifically, the UE monitors paging signals at specific paging occasions of each UE specific paging DRX cycle. The paging occasion is a time interval during which a paging signal is transmitted. The UE has its own paging occasion.

Paging messages are sent on all cells belonging to the same tracking area. If the UE moves from one TA to another TA, the UE sends a Tracking Area Update (TAU) message to the network to update its location.

When the user initially powers on the UE, the UE first searches for the appropriate cell and then remains in RRC IDLE in that cell. When there is a need to establish an RRC connection, the UE held in the RRC _ IDLE establishes a connection with the RRC of the E-UTRAN through an RRC connection procedure and may then transition to RRC _ CONNECTED. The UE remaining in the RRC _ IDLE may need to establish an RRC connection with the E-UTRAN when uplink data transmission is necessary due to a call attempt of a user or the like or when there is a need to transmit a response message when receiving a paging message from the E-UTRAN.

In order to manage mobility of a UE in the NAS layer, two states, an EPS mobility management-registration (EMM-registration) state and an EMM-deregistration state, are defined. These two states apply to the UE and MME. Initially, the UE is in EMM-deregistered state. To access the network, the UE performs a procedure of registering to the network through an initial attach procedure. If the attach procedure is successfully performed, the UE and MME enter the EMM-registration state.

To manage the signaling connection between the UE and the EPS, two types of states are defined: an EPS Connection Management (ECM) -IDLE state and an ECM-CONNECTED state. Two states are applied to the UE and MME. When the UE in the ECM-IDLE state establishes an RRC connection with the E-UTRAN, the UE enters an ECM-CONNECTED state. When the MME in the ECM-IDLE state establishes S1 connection with the E-URTAN, the MME enters the ECM-CONNECTED state. When the UE is in the ECM-IDLE state, the E-UTRAN has no context information about the UE. Accordingly, the UE in the ECM-IDLE state performs a procedure related to UE-based mobility, such as cell selection or reselection, without receiving a command of the network. On the other hand, when the UE is in the ECM-CONNECTED state, the mobility of the UE is managed by a command of the network. If the location of the UE in the ECM-IDLE state becomes different from a location known by the network, the UE reports the location of the UE to the network through a tracking area update procedure.

Hereinafter, Machine Type Communication (MTC) will be described.

Fig. 4 illustrates an example of MTC.

MTC refers to information exchange between MTC UEs 410 via BS 420 without involving human interaction or information exchange between MTC UEs 410 and MTC server 430 via the BS. Services provided by MTC are different from existing communication services that require manual intervention, and MTC provides a wide range of services such as tracking, metering, payment, medical services, remote control, and the like. More specifically, services provided through MTC may include reading meters, measuring water levels, utilizing surveillance cameras, reporting inventory of vending machines, and the like. For convenience, data communication oriented low cost/low specification UEs providing these services are referred to as MTC UEs or low complexity type UEs. The BS may determine whether the UE is an MTC UE based on the capability of the UE. In this specification, MTC UE, low complexity UE, low cost UE, and UE category 0UE may be used in the same meaning, and normal UE may be used to refer to UEs other than the listed UEs.

The MTC server 430 is an entity communicating with the MTC UE 410. The MTC server 430 runs MTC applications and provides MTC specific services to MTC devices. The MTC UE 410 is a wireless device providing MTC communications and may be fixed or mobile.

Since the MTC UE has a small amount of data to be transmitted and occasionally involves uplink/downlink data transmission/reception, it is effective to reduce the cost of the UE and reduce its battery consumption according to a low data transmission rate. MTC UEs are characterized by low mobility and thus have an almost constant channel environment.

MTC UEs do not require high performance functionality and typically use small amounts of data. The concept of UE category 0 was introduced to facilitate the manufacture of low cost MTC UEs. The UE category is a general number used in 3GPP to indicate how much data the UE can handle in the communication modem. Table 1 shows 3GPP UE classes.

[ Table 1]

UE category

DL speed

UL speed

UE category

DL speed

UL speed

0

1Mbps

7

300Mbps

100Mbps

1

10Mbps

5Mbps

8

3Gbps

1.5Gbps

2

50Mbps

25Mbps

9

450Mbps

50Mbps

3

100Mbps

50Mbps

10

450Mbps

100Mbps

4

150Mbps

50Mbps

11

600Mbps

50Mbps

5

300Mbps

75Mbps

12

600Mbps

100Mbps

6

300Mbps

50Mbps

13

400Mbps

50Mbps

Allowing UE class 0 UEs to handle only 1Mbps enables it to manufacture modems without much effort and high cost, and can use only one antenna. Further, UE class 0 UEs are allowed to perform transmission or reception only for a specified time, not to simultaneously perform transmission and reception, and thus can operate in FDD in the same manner as in TDD. In addition, unlike existing TDD, a sufficient switching time of about 1ms can be assigned within the transition period between transmission and reception, thereby significantly reducing the cost of hardware components as a whole, particularly in view of modem and RF.

MTC UEs may be installed not only in buildings and factories, but also in places with limited coverage, such as basements. For example, approximately 20% of MTC UEs supporting MTC services, such as smart metering, may be installed in poor "deep indoor" environments such as basements. Therefore, for successful MTC data transmission, it is necessary to increase the coverage of MTC UEs by about 20dB compared to the coverage of conventional normal UEs. In view of this situation, various coverage enhancement techniques, such as a repetitive transmission method for MTC UEs over each channel/signal, are currently being discussed.

Hereinafter, a cellular internet of things (CIoT) will be described.

The internet of things (IoT) is a future infrastructure and service for future information communication, where all objects are connected to the internet to communicate directly with each other. Although IoT is essential to improve quality of life and productivity on the basis of the super-interconnected society, IoT is ultimately important because it forms the infrastructure of the country and further becomes the central nervous system of humans and the earth. The IoT may be broadly divided into IoT (ciot) -based cellular mobile communication and IoT-based non-cellular mobile communication.

CIoT means IoT based on cellular mobile communication. In order to effectively support the cellular-based IoT service, MTC traffic generated intermittently and sporadically in the form of packets having a short length must be efficiently transmitted. In addition, in the case of an application service with real-time constraints, it is necessary to meet the delay requirement by sending data packets (in license-free form) immediately without having to go through a separate channel allocation procedure. Furthermore, for large-scale random access for IoT services, it is necessary to reduce device cost and power consumption, increase coverage, and improve the efficiency of random access capacity and procedures.

Generally, the main use case of CIoT is the equipment used to send and receive small data packets. Therefore, the requirement to be met by the system may be to efficiently transmit/receive small data packets. For example, when transmitting and receiving small data packets, the battery consumption of the UE must be low. For example, when sending and receiving small data packets, the amount of signaling required in the network and over the air must be reduced.

In the user plane based CIoT, an RRC suspend procedure and an RRC resume procedure have been newly proposed for user data transmission. The eNB may suspend the RRC connection if the eNB no longer has data to send to the UE after establishing the RRC connection with the UE. The RRC connection may be temporarily stopped by an RRC suspension procedure. The eNB may resume the RRC connection if the eNB has data to transmit to the UE after suspending the RRC connection with the UE. The RRC connection may be recovered through an RRC recovery procedure. Furthermore, in user plane based CIoT, Mobility Management (MM) procedures may be re-proposed for Tracking Area Update (TAU).

Hereinafter, a description is given of the number of users for transmission in a user plane based CIoTAccording to the RRC suspend procedure.

Fig. 5 illustrates a suspension procedure of RRC connection in a user plane based CIoT.

The RRC suspend procedure may be used for transition from the RRC _ CONNECTED state to the RRC _ IDLE state. Further, the RRC suspend procedure may enable the UE to enter a context of RRC _ IDLE mode.

Referring to fig. 5, in step S501, the network may determine to suspend the RRC connection.

In step S502, the eNB may indicate to the MME that the RRC connection of the UE has been suspended through a new S1AP message. The new S1AP message may be an S1AP UE context deactivation message. The MME and eNB may store the UE context related to the S1AP association.

In step S503, the MME may send a release access bearer request (abnormal release or "new cause" of radio link indication) message to the S-GW. The release access bearer request message may request release of all S1-U bearers of the UE. The S-GW may consider that the UE has become IDLE state.

In step S504, the S-GW may send a response to the release access bearer request message to the MME.

In step S505, the MME may send an ACK to the eNB for the S1AP UE context deactivation message.

In step S506, the MME may enter an ECM _ IDLE state.

In step S507, the eNB may suspend the RRC connection towards the UE. An identifier may be provided for use after a subsequent resumption of the suspended RRC connection. The identifier may be a "recovery ID".

In step S508, the UE RRC layer may enter an RRC _ IDLE state, and the UE NAS layer may enter an ECM _ IDLE state.

Hereinafter, an RRC recovery procedure for transmitting user data in the user plane-based CIoT is described.

Referring to fig. 6, in steps S601 to S603, the UE follows the conventional procedure, and detailed description thereof is omitted.

In step S604, the UE may transmit msg3 to the eNB. msg3 may be a new RRC connection resume request message. The new RRC connection resume request message may include the UE's resume ID, authentication token, bearer indicator (bearer Ind), and establishment cause. The eNB may use the resume ID to associate the UE that has sent the resume ID with a previously stored UE context.

In step S605, the eNB may transmit an RRC connection recovery complete message to the UE. If RRC connection recovery complete is specified, the network may indicate which DRB has been recovered.

In step S606, the UE and eNB may restore the stored security context.

In step S607, the eNB may notify the MME of the UE status change. The UE may be notified of the state change by a new message. The new message may be an S1AP UE context activity message. The MME may enter the ECM _ CONNECTED state.

In step S608, the MME may send a modify bearer request message to the S-GW for each PDN connection. If the S-GW supports the modify Access bearer request procedure and there is no need for the S-GW to send signaling to the P-GW, the MME may send a modify Access bearer request message to the S-GW for each UE in order to optimize the signaling. The S-GW is now able to send downlink data to the UE. The S-GW may consider that the UE has become CONNECTED state.

In step S609, the S-GW may send a response to the modify bearer request message to the MME. The response may be a modify bearer response message.

In step S610, the MME may send an ACK to the eNB for the S1AP UE context activity message.

If the msg3 already includes the user plane and an indication indicating that all user planes are transmitted, the eNB may suspend the RRC connection and may implicitly indicate that the user plane has been successfully received instead of transmitting the msg4 in step S611.

Hereinafter, MM procedure for TAU in user plane based CIoT is described.

Fig. 7 shows the MM procedure of TAU in CIoT based user plane.

Referring to fig. 7, in steps S701 to S702, the UE follows the conventional procedure, and detailed description thereof is omitted.

In step S703, the UE may transmit msg3 to the eNB. msg3 may be a new RRC connection resume request message. The new RRC connection recovery request message may include a recovery ID of the UE, an authentication token, an establishment cause, and a NAS PDU. The eNB may use the resume ID in order to associate the UE that has sent the resume ID with a previously stored UE context. Additionally, msg3 may include a NAS PDU containing a TAU request. In contrast, unlike the RRC connection resume request message, msg3 may not include a bearer indicator (bearer Ind). The lack of bearer indicators may indicate that only SRBs are necessary for the eNB. If there is insufficient space available to include the TAU request, the flag may indicate a subsequent message including the TAU request in step S705.

In step S704, the eNB may transmit an RRC connection recovery complete message to the UE. The network may complete contention resolution. The RRC connection recovery complete message may include a recovery ID.

If the msg3 does not have enough space to include the TAU request, step S705 may be performed.

In step S706, the eNB may deliver the TAU request to the MME. The TAU request may be included in the S1AP initial UE message.

In step S707, the MME may transmit a TAU accept to the eNB. The TAU accept may be included in the S1AP downlink NAS transport message.

In step S708, the eNB may transmit a TAU accept to the UE. The TAU accept may be included in the DL information transfer message.

In step S709, the eNB may transmit an RRC suspend message to the UE. Thus, the RRC connection may be suspended. The RRC suspend message may include a resume ID.

As described in step S703, in case of the current user plane-based CIoT, the UE transmits an RRC connection recovery request message that does not include "bearer ind. In general, since the UE does not transmit UL data during TAU, this indicates that recovery of the bearer context is not necessary when the eNB transmits a TAU request to the MME. When the eNB receives the RRC connection resume request message, the eNB does not transmit the UE context activity message, but may transmit an initial UE message including a TAU request. In this specification, the UE context active message may be used as the same concept as the UE context restoration request message.

If UL data exists when the UE in the ECM _ IDLE state triggers the TAU procedure, the UE may transmit an RRC connection resume request message including a TAU request, and an active flag. In this case, since the RRC connection resume request message does not include "bearer ind. Therefore, in order for the UE to transmit UL data, the UE must perform an RRC recovery procedure after the MM procedure is completed and the UE transitions to the RRC _ IDLE state. Therefore, for RRC suspend and RRC resume, unnecessary signaling may occur in the Uu interface, and unnecessary transition of the UE to the RRC state may occur.

Although the TAU request without the active flag is considered in the MM procedure, there may be a problem in that the RRC recovery procedure must be performed. In CIoT, the UE may deactivate Access Stratum (AS) functions of the UE and enter a Power Save Mode (PSM). When the MME receives the TAU request message without the active flag, although the MME recognizes that DL data to be transmitted to the UE exists, the MME cannot transmit the DL data to the UE. The reason is that the bearer context for DL data transmission is not activated according to the MM procedure.

Therefore, in order to solve the problem, a method of configuring a bearer for transmission of user data in a user plane-based cellular internet of things (CIoT) and an apparatus supporting the same according to an embodiment of the present invention are described.

When the MME receives the TAU request message including the active flag, the MME may notify the eNB of the specific indication. The TAU request message including the active flag is sent by the UE and may be sent to the MME via the eNB. With a specific indication, the MME may instruct the eNB to refrain from suspending the RRC connection and resume the RRC connection.

Alternatively, although the MME does not receive the TAU request message including the active flag, the MME may notify the eNB of a specific indication when the MME recognizes that downlink data to be transmitted to the UE exists. With a specific indication, the MME may instruct the eNB to refrain from suspending the RRC connection and resume the RRC connection.

Referring to fig. 8, in step S800, the UE may be in an RRC _ IDLE state.

In step S801, the UE may transmit a random access preamble to the eNB.

In step S802, the eNB may transmit a response to the random access preamble to the UE. The response to the random access preamble may be a random access response.

In step S803, the UE may transmit an RRC connection recovery request message to the eNB. The RRC connection resume request message may not include a bearer indicator (bearer Ind). In contrast, the RRC connection restoration request message may include a TAU request message. Also, the TAU request message may have an active flag.

In step S804, the eNB may transmit an RRC connection recovery complete message to the UE in order to complete contention resolution.

In step S805, the eNB may deliver a TAU request message to the MME based on the received RRC connection resumption request message without the bearer indicator. The TAU request message may be delivered using an initial UE message.

In step S806, when the MME receives the message from the eNB, the MME may recognize whether the TAU request message includes an active flag and whether there is downlink data to be transmitted to the UE.

If the TAU request message includes an active flag, the MME may send a specific indication to the eNB. Alternatively, if there is downlink data to be transmitted to the UE, the MME may transmit a specific indication to the eNB. The specific indication may be included in a downlink NAS transport message. Further, the downlink NAS transport message may include a TAU accept message.

The specific indication may indicate that the RRC connection should not be suspended and that the UE context restoration request message should be triggered. That is, suspension of the RRC connection may be prohibited, and transmission of the UE context restoration request message may be triggered by a specific indication. The specific indication may inform the eNB that the stored S1AP association and/or S1-U bearer context related information should be restored.

In step S807, the eNB may deliver a TAU accept message to the UE. The TAU accept message may be delivered using a DL info transfer message. The eNB may inform the UE which DRB is resumed through a DL information transfer message based on a specific indication from the MME.

In step S808, the UE and eNB may restore the stored security context.

In step S809, the eNB may transmit a UE context restoration request message to the MME based on the specific indication received in step S806. The UE context restoration request message may be a UE context activity message.

In step S810, the MME may modify the bearer together with the S-GW.

In step S811, the MME may transmit a UE context restoration response message to the eNB as a response to the UE context restoration request message. The UE context restoration response message may be a UE context activity confirm message.

The eNB may inform the MME whether recovery for the UE is possible. Further, when the MME receives the TAU request message including the active flag, the MME may provide an indicator to the eNB to trigger the UE context restore request message.

Alternatively, the eNB may inform the MME whether recovery for the UE is possible. Further, if there is downlink data to be sent to the UE, the MME may provide an indicator to the eNB to trigger the UE context restoration request message.

Referring to fig. 9, in step S900, the UE may be in an RRC _ IDLE state.

In step S901, the UE may transmit a random access preamble to the eNB.

In step S902, the eNB may transmit a response to the random access preamble to the UE. The response to the random access preamble may be a random access response.

In step S903, the UE may transmit a resume request indication requesting resumption for the UE to the eNB. For example, the UE may send a recovery ID to the eNB. The recovery request indication may be included in the RRC connection request message.

In step S904, when the eNB receives the RRC connection request message from the UE, the eNB may check that recovery of the previously suspended RRC connection with the UE is possible based on the recovery request indication.

In step S905, the eNB may transmit an RRC connection setup message to the UE.

In step S906, the UE may transmit an RRC connection setup complete message to the eNB as a response to the RRC connection setup message. The RRC connection setup complete message may include a TAU request message. The TAU request message may have an active flag.

In step S907, the eNB may deliver the TAU request message to the MME. The TAU request message may be delivered using an initial UE message. Further, the initial UE message may include a recoverable indication. The recoverable indication may inform the MME whether recovery of a previously suspended RRC connection with the UE is possible.

In step S908, when the MME receives the message from the eNB, the MME may identify whether the TAU request message includes an active flag and whether there is downlink data to be transmitted to the UE.

If the TAU request message includes an active flag, the MME may send a resume indication to the eNB. Alternatively, if there is downlink data to be transmitted to the UE, the MME may transmit a resume indication to the eNB. The recovery indication may be included in the downlink NAS transport message. Further, the downlink NAS transport message may include a TAU accept message.

The recovery indication may indicate that the UE context recovery request message should be triggered. That is, the transmission of the UE context restoration request message may be triggered by the restoration indication. The UE context restoration request message may be a UE context activity message. The resume indication may inform the eNB that the stored S1AP association and/or S1-U bearer context related information should be resumed.

If the TAU request message does not include an active flag and there is no downlink data to send to the UE, the MME may send a downlink NAS transport message to the eNB that does not include a recovery indication.

In step S909, the eNB may transmit a TAU accept message to the UE. The TAU accept message may be transmitted using a DL info transfer message. The eNB may inform the UE which DRB is recovered through a DL information transfer message based on the recovery indication from the MME.

In step S910, the eNB may transmit a UE context restoration request message to the MME based on the restoration indication received in step S908. The UE context restoration request message may be a UE context activity message.

In step S911, the MME may modify the bearer together with the S-GW.

In step S912, the MME may transmit a UE context restoration response message to the eNB as a response to the UE context restoration request message. The UE context restoration response message may be a UE context activity confirm message.

If the eNB is aware that the RRC connection setup triggered by the UE has been initiated via mo-signaling, the eNB may send a TAU request message to the MME using a UE context restore request message. Further, the MME may provide the TAU accept message to the eNB using the UE context restore response message. The UE context restoration request message may be a UE context activity message. The UE context restoration response message may be a UE context activity accept message.

Referring to fig. 10, in step S1000, the UE may be in an RRC _ IDLE state.

In step S1001, the UE may transmit a random access preamble to the eNB.

In step S1002, the eNB may transmit a response to the random access preamble to the UE. The response to the random access preamble may be a random access response.

In step S1003, the UE may transmit an RRC connection restoration request message including an establishment cause with mo-signaling to the eNB. Alternatively, the UE may transmit an RRC connection request message including the establishment cause with mo-signaling to the eNB. If the RRC connection request message is used for recovery, the RRC connection request message may include an indication requesting recovery of the UE.

In step S1004, upon receiving the RRC connection resume request message from the UE, the eNB may recognize whether resume is possible. If recovery is possible and the establishment cause is marked as mo-signaling, the eNB must defer transmission of the UE context recovery request message until receiving a NAS message from the UE including a UL information transfer message or an RRC connection setup complete message. To indicate whether recovery is possible, the eNB may transmit an RRC connection recovery complete message or an RRC connection setup message to the UE.

In step S1005, if recovery is possible, the UE may transmit a TAU request message to the eNB. The TAU request message may be included in a UL information transfer message or an RRC connection setup complete message.

In step S1006, the UE and eNB may restore the stored security context.

In step S1007, the eNB may transmit a TAU request message to the MME based on step S1004. The TAU request message may be included in the UE context restoration request message. The UE context restoration request message may be a UE context activity message.

In step S1008, the MME may modify the bearer together with the S-GW.

In step S1009, the MME may transmit a UE context restoration response message to the eNB as a response to the UE context restoration request message. The UE context restoration response message may include a TAU accept message. The UE context restoration response message may be a UE context activity confirm message.

In step S1010, the eNB may deliver a TAU accept message to the UE. The TAU accept message may be delivered using a DL info transfer message.

When the MME receives the TAU request message including the active flag, the MME may inform the eNB that the previously stored UE context should be activated. Alternatively, if there is downlink data to be transmitted to the UE, the MME may notify the eNB that the previously stored UE context is activated.

Referring to fig. 11, in step S1100, the UE may be in an RRC _ IDLE state.

In step S1101, the UE may transmit a random access preamble to the eNB.

In step S1102, the eNB may transmit a response to the random access preamble to the UE. The response to the random access preamble may be a random access response.

In step S1103, the UE may transmit an RRC connection request message to the eNB.

In step S1104, the eNB may transmit an RRC connection setup message to the UE.

In step S1105, the UE may transmit an RRC connection setup complete message to the eNB as a response to the RRC connection setup message. The RRC connection setup complete message may include a TAU request message. The TAU request message may have an active flag.

In step S1106, the eNB may deliver a TAU request message to the MME. The TAU request message may be delivered using an initial UE message.

In step S1107, upon receiving the message from the eNB, the MME may identify whether the TAU request message includes an active flag and whether there is downlink data to be transmitted to the UE.

If the TAU request message includes an active flag, the MME may identify whether the eNB that has transmitted the initial UE message suspends the UE context for the UE that has transmitted the TAU request message in step S1106. Alternatively, if there is downlink data to be transmitted to the UE, the MME may identify whether the eNB having transmitted the initial UE message in step S1106 is suspending the UE context for the UE having transmitted the TAU request message. The TAU request message may be sent by the UE through an RRC connection suspend procedure. If any of the items listed below appear in the MME, the MME can identify that the eNB is suspending the UE context.

(1) During suspension of the RRC connection with the UE, the MME stores and suspends information for the UE context of the UE on the eNB.

(2) Tunnel endpoint id (teid) assigned by eNB during procedure for RRC suspension.

When the MME identifies that the UE context for the UE to which the eNB has sent the TAU request message has been suspended, the MME may modify the bearer with the S-GW. If not, the MME may perform existing TAU procedures. If the TAU request message does not include an active flag and there is no downlink data to send to the UE, the MME may perform an existing TAU procedure without modifying the bearer.

In step S1108, if the TAU request message includes an active flag or that downlink data to be transmitted to the UE exists and thus the MME identifies that the eNB has stored a UE context for the UE that has requested TAU (in step S1107), the MME may transmit a UE context activation indication to the eNB indicating activation of the previously stored UE context. The UE context activation indication may be included in a downlink NAS transport message. Further, the downlink NAS transport message may include a TAU accept message.

If the TAU request message does not include an active flag and there is no downlink data to send to the UE, the MME may send a downlink NAS transport message to the eNB that does not include a UE context activation indication. In this case, no bearer modification is performed.

In step S1109, the eNB activates the previously stored UE context when receiving a message from the MME. Further, the eNB may deliver a TAU accept message to the UE. The TAU accept message may be delivered using a DL info transfer message. The activation of the UE context may be indicated for the UE using a DL information transfer message.

Fig. 12 is a block diagram illustrating a method for an eNB to configure a bearer for transmission of user data in a user plane-based CIoT according to an embodiment of the present invention.

Referring to fig. 12, in step S1210, an eNB may receive a Tracking Area Update (TAU) request message from a UE. The UE may be in an RRC IDLE state.

In step S1220, the eNB may transmit an initial UE message including a TAU request message to a Mobility Management Entity (MME).

In step S1230, the eNB may receive a downlink NAS transport message including the recovery indication from the MME.

In step S1240, the eNB may transmit a UE context restoration request message to the MME based on the restoration indication.

The TAU request message received from the UE may be included in the RRC connection resume request message. The RRC connection resumption request message may not include a bearer indication. Suspension of the RRC connection may be prohibited and transmission of the UE context resume request message may be triggered by the resume indication. The recovery indication may further be received from the MME if the TAU request message includes an active flag. Alternatively, the recovery indication may be further received from the MME if the presence of downlink data to be sent to the UE is identified by the MME.

The eNB may receive a resume request indication from the UE to request resumption for the UE, and may determine whether it is possible to resume a previously suspended RRC connection based on the resume request indication. The recovery request indication may be included in the RRC connection request message. The TAU request message received from the UE may be included in an RRC connection setup complete message. The initial UE message may include a recoverable indication indicating whether the eNB may recover a previously suspended RRC connection. The transmission of the UE context restore request message may be triggered by a restore indication.

The recovery indication may further be received from the MME if the TAU request message includes an active flag. Alternatively, the recovery indication may be received from the MME if the MME identifies the presence of downlink data to be sent to the UE.

UE 1300 includes a processor 1301, memory 1302, and a transceiver 1303. The memory 1302 is connected to the processor 1301 and stores various information for driving the processor 1301. The transceiver 1303 is connected to the processor 1301, and transmits and/or receives a radio signal. The processor 1301 implements the proposed functions, procedures, and/or methods. In the above embodiments, the operation of the UE may be implemented by the processor 1301.

BS 1301 includes processor 1311, memory 1312, and transceiver 1313. The memory 1312 is connected to the processor 1311, and stores various information for driving the processor 1311. The transceiver 1313 is connected to the processor 1311, and transmits and/or receives a radio signal. The processor 1311 implements the proposed functions, procedures, and/or methods. In the above embodiments, the operation of the BS may be implemented by the processor 1301.

The MME 1320 includes a processor 1321, a memory 1322, and a transceiver 1323. The memory 1322 is connected to the processor 1321, and stores various information for driving the processor 1321. The transceiver 1323 is connected to the processor 1321, and transmits and/or receives a radio signal. The processor 1321 implements the proposed functions, procedures, and/or methods. In the above embodiments, the operations of the MME may be implemented by the processor 1321.

The processor may include an Application Specific Integrated Circuit (ASIC), a separate chipset, a logic circuit, and/or a data processing device. The memory may include Read Only Memory (ROM), Random Access Memory (RAM), flash memory, memory cards, storage media, and/or other storage devices. The transceiver may include baseband circuitry for processing wireless signals. When the embodiments are implemented in software, the aforementioned methods can be implemented by means of modules (i.e., procedures, functions, and so on) for performing the aforementioned functions. The modules may be stored in a memory and executed by a processor. The memory may be located internal or external to the processor and may be coupled to the processor using a variety of well-known means.

Various methods based on the present description have been described on the basis of the foregoing examples by referring to the drawings and the reference numerals given in the drawings. Although, for purposes of explanation, each method describes multiple steps or blocks in a particular order, the invention disclosed in the claims is not limited by the order of the steps or blocks, and each step or block can be performed in a different order or concurrently with other steps or blocks. In addition, those skilled in the art may appreciate that the present invention is not limited to each of the steps or blocks, and at least one different step may be added or deleted without departing from the scope and spirit of the present invention.

The foregoing embodiments include various examples. It should be noted that it is not possible for a person skilled in the art to interpret all possible combinations of examples, and also to know that various combinations can be derived from the techniques of the present specification. Therefore, the scope of protection of the present invention should be determined by combining various examples described in the detailed explanation without departing from the scope of the claims below.

Claims

1. A method of a base station configuring a bearer for transmission of user data in a user plane based cellular internet of things (CIoT) in a wireless communication system, the method comprising:

receiving an RRC connection recovery request message including a Tracking Area Update (TAU) request message from a User Equipment (UE),

transmitting an initial UE message including the TAU request message to a Mobility Management Entity (MME),

receiving a downlink NAS transport message including a recovery indication from the MME, an

Sending a UE context restore request message to the MME based on the restore indication,

wherein the RRC connection resume request message does not include a bearer indication, an

Wherein suspension of the RRC connection is prohibited and transmission of the UE context resume request message is triggered by a resume indication.

2. The method of claim 1, wherein the recovery indication is received from the MME based on the TAU request message including an active flag.

3. The method of claim 1, wherein the recovery indication is received from the MME based on identification by the MME of the presence of downlink data to be transmitted to the UE.

4. The method of claim 1, further comprising:

receiving, by the base station, a resume request indication from the UE to request resumption of the UE; and

determining whether recovery of a previously suspended RRC connection is possible based on the recovery request indication.

5. The method of claim 4, wherein the recovery request indication is included in an RRC connection request message.

6. The method of claim 5, wherein the TAU request message received from the UE is included in an RRC connection setup complete message.

7. The method of claim 6, wherein the initial UE message includes a recoverable indication indicating whether the base station can recover the previously suspended RRC connection.

8. The method of claim 1, wherein the UE is in an RRC IDLE state.

9. A base station for configuring a bearer for transmission of user data in a user plane based cellular internet of things (CIoT) in a wireless communication system, the base station comprising:

a memory;

a transceiver; and

a processor connected to the memory and the transceiver, wherein the processor is configured to:

control the transceiver to receive an RRC connection recovery request message including a Tracking Area Update (TAU) request message from a User Equipment (UE),

control the transceiver to send an initial UE message including the TAU request message to a Mobility Management Entity (MME),

control the transceiver to receive a downlink NAS transport message including a recovery indication from the MME, an

Control the transceiver to send a UE context restoration request message to the MME based on the restoration indication,